Question

I am trying to match full word from some lines, wanted to know how to use the OR in regex,
If i use only one keyword, it works fine. Example,

regex = ".*\\b" + "KEYWORD1" + "\\b.*";


String regex = ".*\\b" + "KEYWORD1|KEYWORD2|KEYWORD3" + "\\b.*";

    for (int i = start; i < end; i++) {           
        if (lines[i].matches(regex)) {
            System.out.println("Matches");
        }
    }

Answer 1

You want:

String regex = ".*\\b(KEYWORD1|KEYWORD2|KEYWORD3)\\b.*";

Originally, your regex was being evaluated like this:

.*\bKEYWORD1
|
KEYWORD2
|
KEYWORD3\b.*

But you want:

.*\b
(
    KEYWORD1
    |
    KEYWORD2
    |
    KEYWORD3
)
\b.*

This cool tool can help you analyse regexes and find bugs like this one.